Various loads mounted on vehicles are connected to batteries through wires, connectors, junction blocks, relay blocks, electronic switches such as semiconductor switches, and the like. In such a load circuit, it is necessary to check whether the load is normally connected to the electronic switch. Specifically, disconnection of wires and poor connection of connectors occur in some cases (hereinafter, disconnection, poor connection, and open-circuit faults are collectively referred to as disconnection). In such a case, the load circuit cannot be normally operated. Accordingly, some disconnection detectors for detecting disconnection of load circuits have been proposed and put into practical use.
The conventional disconnection detectors employ a method of detecting disconnection using a current detection circuit for detecting disconnection provided for a load circuit (see PTL 1) or a method of detecting disconnection by providing a shunt resistor for a load circuit and measuring voltage generated across the shunt resistor.